A wide variety of natural and synthetic filling materials for thermal insulation applications, such as outerwear apparel, e.g. jackets, stocking caps, and gloves, sleeping bags and bedding articles, e.g., pillows, comforters, quilts, and bedspreads, are known.
Natural feather down has found wide acceptance for thermal insulation applications, primarily because of its outstanding weight efficiency, softness, and resiliency. Properly fluffed and contained within an article or garment, down is generally recognized as the insulation material of choice. However, down compacts and loses its insulating properties when it becomes wet and can exhibit a rather unpleasant odor when exposed to moisture. Also a carefully controlled cleaning and drying process is required to restore the fluffiness and resultant thermal insulating properties to an article in which the down has compacted.
There have been numerous attempts to prepare synthetic fiber-based structures having the characteristics and structure of down. Several attempts have been made to produce substitutes for down by converting the synthetic fibrous materials into insulating batts configured to have fibers that have specific orientations relative to the faces of the batt followed by bonding of the fibers to stabilize the web to afford improved insulating properties.
Such attempts include a pillow formed of an assemblage of generally co-planar fibers encased in a casing, where the fibers are substantially perpendicular to the major axis of the elliptical cross-section of the pillow surfaces to provide a degree of resiliency and fluffability; a thermal insulating material which is a web of blended microfibers with crimped bulking fibers which are randomly and thoroughly intermixed and intertangled with the microfibers to provide high thermal resistance per unit thickness and moderate weight; and a nonwoven thermal insulating batt of entangled staple fibers and bonding staple fibers which are substantially parallel to the faces of the web at the face portions of the web and substantially perpendicular to the faces of the batt in the central portion of the batt with the bonding staple fibers bonded to the structural staple fibers and other bonding staple fibers at points of contact.
Other structures include a blend of 80 to 90 weight percent of spun and drawn, crimped staple synthetic polymeric microfibers having a diameter of 3 to 12 microns and 5 to 20 weight percent of synthetic polymeric staple macrofibers having a diameter of from more than 12 up to 50 microns which is described as comparing favorably to down in thermal insulating properties and a synthetic fiber thermal insulating material in the form of a cohesive fiber structure of an assemblage of from 70 to 95 weight percent of synthetic polymeric microfibers having diameter of from 3 to 12 microns and from 5 to 30 weight percent of synthetic polymeric macrofibers having a diameter of 12 to 50 microns where at least some of the fibers are bonded at their contact points, the bonding being such that the density of the resultant structure is within the range of 3 to 16 kg/m.sup.3, the thermal insulating properties of the bonded assemblage being equal to or not substantially less than the thermal insulating properties of the unbonded assemblage. In this assemblage the entire assemblage is bonded together to maintain support and strength to the fine fibers without suffering from the lower thermal capacity of the macrofiber component.
A still further structure suggested for providing a resilient, thermally bonded non-woven fibrous batt includes having uniform compression modulus in one plane which is more than the compression modulus measured in a direction perpendicular to that plane and a substantially uniform density across its thickness. The batt is prepared by forming a batt comprising at least 20% by weight of crimped and/or crimpable conjugate fibers, i.e., bicomponent bonding fibers, having or capable of developing a crimp frequency of less than 10 crimps per extended cm, and a decitex in the range of 5 to 30. The batt is thermally bonded by subjecting it to an upward fluid flow heated to a temperature in excess of the softening component of the conjugate fiber to effect inter-fiber bonding.